James McNamara, Sensata Technologies
Originally developed for audio speakers, voice coil actuation technology is now being utilized to provide precise and reliable motion control for a wide range of medical applications.
Although it has been around for decades, VCA technology is still a mystery to many design engineers as, until recently, the application spaces for which it was a cost-effective solution were relatively restricted. Many designers had to settle for more traditional, but less flexible, solenoid-based devices. Now that powerful microcontrollers (MCUs) and precise and efficient drivers are readily available, advanced linear motion designs using VCAs are easier and less expensive to implement.Any time an engineer is looking at developing a product that requires highly reliable, highly repeatable and highly controllable motions, they need to consider VCA.
VCAs offer many benefits to the medical design engineer. They are very simple and extremely robust, yet are as exactly precise as the input given them. VCAs accelerate smoothly and quickly to any position within their stroke with nearly zero hysteresis and are only limited by the system’s position-sensing precision and driver capability. Because of this accuracy, these devices lend themselves extremely well to applications such as medical devices, robotics and industrial process equipment.
Precision control for medical devices
One application area that demands critical precision is the medical industry. Devices like drug-dispensing pumps and ventilators do not work on approximations — every microliter of liquid (or air) has to be carefully measured and managed. The precise motion control a VCA-based solution provides in a medical flow-management system increases accuracy without complexity or bulk.
The challenges in designing medical devices are compounded beyond strict performance and regulatory standards; there is also the need for small and lightweight devices to allow for portable use by caregivers moving room-to-room in a facility. This demand for performance in a constrained space lends itself well to a VCA solution.Linear voice coil actuators can be designed to meet the ultra-small size and exacting motion control requirements needed in the medical industry. These compact VCAs are often used to control inhalation and exhalation valves on ventilators to provide the exact amount of air specified and the necessary reliability for life-critical applications.
Small VCAs measure just 0.75 in. in diameter and weigh only 2.3 ounces, yet can deliver a peak force of nearly 2 lbs. in an operating stroke of ±2 mm with low hysteresis, zero cogging, high acceleration and a long-life cycle. This accurate linear motion control can also serve other precision medical systems like anesthesia machines as well as ultrasound probes, blood analyzers, and lab equipment.
Development tools to help the medical design engineerDesign tools that aid the engineer in understanding and implementing any given technology are critical to its adoption, and VCAs are not exempt. Self-contained kits like Sensata’s Voice Coil Actuator Developer’s Kit – which include a VCA with a built-in feedback sensor and a programmable controller with PC-compatible motion control software – allow users to take advantage of the benefits of VCAs without needing to specify the electronics required for a complete control system. This type of tool can help designers quickly develop an actuation system and demonstrate a working design with velocity, position, force, reciprocation and acceleration control to address nearly any application.
James McNamara is a senior applications engineer at Sensata Technologies, where he is an expert on voice coil actuator technology. He has been with the company for 12 years and has 40 years of experience working in the electric motor industry. McNamara holds a BS degree from National University in Computer Science.
The opinions expressed in this blog post are the author’s only and do not necessarily reflect those of Medical Design and Outsourcing or its employees.